All prophets came with message of **Tawheed**. What differed is the **legislation(Sharia)**. Anyone who believed in the message of Tawheed and followed their respective prophets would be eligible to enter Jannah.

Below Hadith indicates Jannah will be occupied not only by the nation of Muhammed(ﷺ). Other nations as well will occupy. 

> The Prophet (ﷺ) said, "Allah will say (on the Day of Resurrection), 'O
> Adam.' Adam will reply, 'Labbaik wa Sa`daik', and all the good is in
> Your Hand.' Allah will say: 'Bring out the people of the fire.' Adam
> will say: 'O Allah! How many are the people of the Fire?' Allah will
> reply: 'From every one thousand, take out nine-hundred-and
> ninety-nine.' At that time children will become hoary headed, every
> pregnant female will have a miscarriage, and one will see mankind as
> drunken, yet they will not be drunken, but dreadful will be the Wrath
> of Allah." The companions of the Prophet (ﷺ) asked, "O Allah's
> Apostle! Who is that (excepted) one?" He said, "Rejoice with glad
> tidings; one person will be from you and one-thousand will be from Gog
> and Magog." The Prophet (ﷺ) further said, "By Him in Whose Hands my
> life is, hope that **you will be one-fourth of the people of
> Paradise.**" We shouted, "Allahu Akbar!" He added, "I hope that you
> will be one-third of the people of Paradise." We shouted, "Allahu
> Akbar!" He said, "I hope that you will be half of the people of
> Paradise." We shouted, "Allahu Akbar!" He further said, "You (Muslims)
> (compared with non Muslims) are like a black hair in the skin of a
> white ox or like a white hair in the skin of a black ox (i.e. your
> number is very small as compared with theirs). [Sahih al-Bukhari
> 3348][1]


  [1]: https://sunnah.com/bukhari:3348


> Ibn Abbas reported: The Messenger of Allah, peace and blessings be
> upon him, said, “I was shown the nations before me and one or two
> prophets would pass by with only a few followers, another would pass
> by with none at all. **Then a large crowd of people passed in front of
> me and I said: Is this my nation? It was said: No, this is Moses and
> his people.** Then it was said: Look at the horizon. Behold, there was
> a multitude of people filling the horizon. It was said to me: This is
> your nation from which seventy thousand will enter Paradise without
> reckoning.”
> 
> Source: Ṣaḥīḥ al-Bukhārī 5378, Ṣaḥīḥ Muslim 220